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Expert Evidence in Medical Malpractice Claims

As discussed in an earlier blog post, to be successful in an action for medical malpractice a plaintiff must prove:

  1. That the defendant owed them a duty of care;
  2. That the defendant breached the standard of care;
  3. That the plaintiff suffered an injury and damages; and
  4. That the defendant’s breach of the standard of care caused the plaintiff’s injury and damages.

It is commonly accepted that a healthcare provider owes a duty of care to his or her patient. A plaintiff often requires expert evidence to prove each of the other three elements.

Standard of Care:

In order to establish a breach of the standard of care, the plaintiff must establish that the defendant fell below the standard of a reasonably prudent healthcare practitioner. In many cases, expert evidence is required to speak to what this standard is. This often means retaining a medical practitioner from the same or similar field of expertise to write a report about the standards expected of a reasonably prudent healthcare professional and whether those standards were met. For example, an orthopedic surgeon may be retained to provide an expert opinion in a case involving a knee surgery.

As discussed by Topolniski J in Skinner v Matheson, 2017 ABQB 342 at para 24: “A trial judge evaluates the standard of care of a professional with the assistance of expert evidence on the standards and practices of that discipline”.  However, the determination of what the standard of care requires is a question of law to be decided by the judge. Therefore, as Renke J held in DD v Wong Estate, 2019 ABQB 171 at para 213, while the determination of what the standard of care requires “is informed by expert evidence it is not fixed by medical evidence.” That is, it is the judge’s role to come to a determination as to what the standard of care required, and “the Court can accept all, none, or some of the experts’ evidence” on this point. Often, the plaintiff and defendant adduce conflicting expert opinions, and it is for the judge to weigh these opinions, in conjunction with all of the evidence, to determine what was required by the standard of care.

Sometimes, on rare occasions, expert evidence will not be necessary to establish a breach of the standard of care. This was discussed by the Supreme Court of Canada in ter Neuzen v Korn, 1995 CanLII 72 wherein the Court held at para 55 that, if the issue can be decided based upon the ordinary common sense of the trier of fact, the court can set the appropriate standard of care without resort to expert evidence. This may be the case, for example, where a sponge is left inside a patient following surgery.


The plaintiff has the burden of establishing that the defendant’s breach of the standard of care caused his or her injuries. This often concerns highly technical medical matters and requires the resort to expert evidence from qualified medical experts. The field of expertise will be highly dependent on the facts of the case. However, the courts take a robust and pragmatic approach to causation and do not require the plaintiff to adduce positive scientific proof.  This means that although relevant, “the presence or absence of opinion evidence from an expert positing (or refuting) a causal link is not, therefore, determinative of causation”.


A plaintiff will often retain several experts to ascertain the extent of his or her injuries and the impact of same on the plaintiff’s life. In a complex medical malpractice case this often requires undergoing several in person assessments with qualified medical practitioners who can determine the plaintiff’s needs for rehabilitation, adaptive equipment, care, and assistive supports. This may include, but is not limited to, occupational therapists, physiotherapists, speech language pathologists, life care planners, physiatrists, and neuropsychologists. The assessments required will depend on the facts of the given case.

The plaintiff will often also need to retain an expert economist or accountant to quantify the plaintiff’s past losses including loss of income and cost of care, as well as the cost of the plaintiff’s future care needs and income loss based on the assessment reports of the above mentioned experts.

Once the plaintiff has undergone assessments by the experts his or her counsel retained, the defendant is entitled to retain his or her own corresponding experts to assess the plaintiff. The defendant will also often retain his or her own economist to assess the value of the plaintiff’s losses. All of this evidence will be weighed by the court in quantifying the plaintiff’s damages.

This blog post is intended to provide the reader with a very brief overview of the use of expert evidence in medical malpractice claims. Should you have any questions about medical malpractice claims you may contact one of our lawyers here


Peppler Estate v Lee, 2019 ABQB  144 at para 184

Snell v Farrell, 1990 CanLII 70

British Columbia (Workers’ Compensation Appeal Tribunal) v Fraser Health Authority, 2016 SCC 25 at para 38


By: Iman Jomha